Page:Popular Science Monthly Volume 12.djvu/779

Rh the fed side. The seeds being ripe at the beginning of September, all the flower-stems were gathered, and the plants of three plates were picked out of the moss and carefully washed. The other three plates were left undisturbed: the relative number of plants which will appear in the spring on their "fed" and "starved" sides will be a means of estimating the relative quantities of reserve material stored up. Mr. Darwin gives in the following table the results of counting, measuring, and weighing, the various parts of the two sets of plants:

New Process of Sugar-Manufacture.—Mention is made in the Revue Scientifique of a new process for sugar-manufacture, invented by Prof. Loewig, of Breslau, which greatly simplifies the work. Instead of using lime to defecate the liquor, then having recourse to a double carbonization by carbonic acid, with a view to eliminate this lime in the shape of lime carbonate, and lastly filtering the carbonated liquor through animal charcoal—processes which allow about one-third of the beet-sugar to be transformed into molasses.—Loewig simply adds to the crude liquor hydrate of alumina which he has discovered the means of preparing on the large scale. This hydrate of alumina retains the coloring albuminoid and nitrogenized matters, forming with them a black scum which is removed. All that remains to be done is to concentrate the almost absolutely pure sugary liquid which remains. If this process proves successful, it will revolutionize the sugar-manufacture.

Intensity of Different Colored Lights.—Prof. O. M. Rood describes, in the American Journal of Science. a simple method devised by him for comparing the intensities of light of different colors—a problem that has long been considered one of the most difficult in photometry. To measure the luminosity of vermilion, for example, he attaches a circular disk of vermilion cardboard to the axis of a rotation apparatus, a smaller circular disk of black-and-white cardboard being simultaneously fastened in the same axis, so that by varying the relative proportions of the latter a series of grays might be produced at will. First the compound black-and-white disk is so arranged that, on rotating the machine, a gray decidedly darker than the vermilion is produced. Then the gray is gradually lightened, till the observer becomes doubtful as to which is the more luminous, the gray or the vermilion; the angle occupied by the white sector is then measured. Next, a decidedly more luminous gray is compared with the vermilion, and its luminosity gradually diminished till again there is doubt as to which of the two, the gray or the vermilion, is the more luminous; and then, again, the white sector is measured. The mean of ten such experiments showed that when the luminosity of both disks was the same, the white sector of the black-and-white disk was 23.8 of its whole area, and hence that the luminosity of the vermilion cardboard was in the same ratio, namely, 23.8 per cent, to white. Proper allowance was made by Prof. Rood for the amount of white light reflected by the black disk. The relative luminosity of other colors may, of course, be ascertained in the same way.

Causes of the Chinese Famine.—According to a correspondent of the London Spectator, Frederick H. Barbour, the famine now prevailing in the northern provinces of China began in the fall of 1875. Its immediate cause was the long absence of rain, but the phenomenon to which it was and still is primarily due is the gradual desiccation of the vast plains of Chi-li and Shang-Tung, a process which, commencing in the table-lands of Central Asia, has now reached the densely-peopled northern provinces of China. Mr. Barbour has for the last two years been in constant communication with the famine-stricken districts, and the letters